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CHEVROLET has made its new air-suspension system easily interchangeable in production line assembly with standard full-coil suspension by adopting a 4-link-type rear suspension with short and long arms. A feature of the system is the mounting of the leveling valves within the air-spring assemblies. These valves correct riding height continually at a moderate rate, regardless of whether the springs are leveling or operating in ride motion. The system provides constant frequency ride—ride comfort remains the same whether the car is occupied by the driver alone or is fully loaded.

Fundamental differences exist between sheet metal forming and hydroforming processes. Sheet metal forming is basically a one step metal fabrication process. Almost all plastic deformation of an originally flat blank is introduced when the punch is moved normal to a clamped sheet metal. Hydroforming, however, consists of multiple steps of tube making, pre-bending, crushing, pressurization, etc. Each of the above mentioned steps can introduce permanent plastic deformations. The forming limit diagram obtained for sheet metal forming may or may not be used in hydroforming evaluations. A failure criterion is proposed for predicting bursting failures in tube hydroforming. The tube material's stress-strain curve, obtainable from uniaxial tensile test and subjected to some postulations under large stress/strain states, is used in judging the failure.

This paper discusses an analytical technique for computing the failure rate of steel springs used in automotive part applications. Preliminary computations may be performed and used to predict spring failure rates quickly at a very early stage of a product development cycle and to establish program reliability impact before commitment. The analytical method is essentially a combination of various existing procedures that are logically sequenced to compute a spring probability of failure under various operational conditions. Fatigue life of a mechanical component can be computed from its S-N curve. For steels, the S-N curve can be approximated by formulae which describe the fatigue life as a function of its endurance limit and its alternating stress. Most springs in service are preloaded and the actual stress fluctuates about a mean level. In order to compute an equivalent alternating stress with zero mean, an analytical method based on the Goodman Diagram is used.

Contamination protection of brake rotors has been a challenge for the auto industry for a long time. As contamination of a rotor causes corrosion, and that in turn causes many issues like pulsation and excessive wear of rotors and linings, a rotor splash protection shield became a common part for most vehicles. While the rotor splash shield provides contamination protection for the brake rotor, it makes brake cooling performance worse because it blocks air reaching the brake rotor. Therefore, balancing between contamination protection and enabling brake cooling has become a key critical factor when the splash shield is designed. Although the analysis capability of brake cooling performance has become quite reliable, due to lack of technology to predict contamination patterns, the design of the splash protection shield has relied on engineering judgment and/or vehicle tests. Optimization opportunities were restricted by cost and time associated with vehicle tests.

This paper describes a test of 2500 General Motors passenger cars equipped with anti-lacerative windshields and driven in rental fleets. It also de840391 scribes the laboratory tests conducted prior to the fleet installation of the test windshields. Evaluation of haze development caused by abrasion of the anti-lacerative surface will take several more years of exposure. Other test results have been encouraging, except for the difficulties encountered in the removal of stickers and decals from the inner surface.

By-wire systems have the potential of augmenting the normal capabilities of human drivers as well as serving as enablers for emerging safety technologies. To achieve these features, these systems must be carefully designed, analyzed, and verified for safety because they are new, complex, and potentially exhibit new and different failure modes and effects. Duplication may be required to ensure that safety margins are met in the presence of faults. Full duplication of every system may not lead to a cost effective implementation, especially if multiple independent by-wire systems are placed on a single vehicle. Other architectural approaches for the integration of by-wire systems need to be considered and analyzed. These architectures should meet if not exceed the safety requirements while providing a more cost effective implementation than a fully duplicated architecture.

As a result of raised awareness regarding the proliferation of individual OEM recommended ATFs, and discussion in various forums regarding the possibility of ‘universal’ service fill fluids, it was decided to study how divergent individual OEM requirements actually are by comparing the fluids performance in industry standard tests. A bench-mark study was carried out to compare the performance of various OEM automatic transmission fluids in selected industry standard tests. All of the fluids evaluated in the study are used by certain OEMs for both factory and service fill. The areas evaluated included friction durability, oxidation resistance, viscosity stability, aeration and foam control. The results of this study are discussed in this paper. Based on the results, one can conclude that each ATF is uniquely formulated to specific OEM requirements.

The level of filtration in an engine can have a significant impact on wear rates due to abrasive particles. Tests were conducted to establish a relationship between the level of filtration and abrasive engine wear. Although the tests were run in a laboratory environment, wear was reduced by as much as 70% by going from a 40 micron filter to a 15 micron filter. Testing was performed on a heavy duty diesel engine and later with an automotive gasoline engine. The results from both engines were consistent and showed that the relationship developed can be applied to nearly any internal combustion recipricating engine.

Casting technology developmentshave led to a manufacturing process that allows the casting of thin wall (2-3mm) heat resistant ferritic stainless steel exhaust manifolds which can replace stamped and tubular weldments as well as iron castings where temperature requirements are increased. This casting process combines the thin wall and clean metal benefits of the counter gravity, vacuum-assist casting process using thin, light-weight bonded sand molds supported by vacuum-ridgidized sand. This combination is called the LSVAC (Loose Sand Vacuum Assisted Casting) process, a patented process. This process will significantly contribute to the growth of near-net shape steellstainless steel castings for automotive and allied industries. For exhaust manifolds, a modified grade of ferritic stainless steel with good oxidation resistance to 950°C in high dew point synthetic exhaust gas atmospheres was developed.

Electro-Motive Division of GM jointly with HRL Laboratories have developed a software tool, called TechPro, which assists in troubleshooting of diesel locomotives. The tool has been tested extensively in the field for the last two years. It has improved significantly the quality of diagnosis of locomotives. The tool is based on Graphical Probabilistic Models and Case Data Bases. We will discuss the design of the tool, its performance and will show its relevance to diagnosis of automobiles.

Life Cycle Assessments (LCA) of complex systems, such as vehicles and vehicle components, are based on the quantification of the energy, wastes, and emissions associated with the material production, manufacturing, use and end of life of the product. However, the volume of information needed to provide a comprehensive assessment of the environmental burdens is large and complicates the decision process in choosing among alternatives. For this reason people have attempted to simplify the information by collapsing it into a single index, which essentially assigns a score to a product of being “good” or “bad”. Even though such an approach looks attractive to the decision-makers that want simple answers based on meaningful data, the results may be misleading.

Casting, machining and structural simulations were completed on a V8 engine block made in Compacted Graphite Iron (CGI) for use in a racing application. The casting and machining simulations generated maps of predicted tensile strength and residual stress in the block. These strength and stress maps were exported to a finite element structural model of the machined part. Assembly and operating loads were applied, and stresses due to these loads were determined. High cycle fatigue analysis was completed, and three sets of safety factors were calculated using the following conditions: uniform properties and no residual stress, predicted properties and no residual stress, and predicted properties plus residual stress.

Commercially available software tools are widely used to assist in conducting life cycle inventory, life cycle assessment (LCA), life cycle impact analysis (LCIA), and design for the environment (DfE) studies. Five leading software tools, Boustead 4.2, GaBi 3.2, SimaPro 4.0, TEAM 3.0, and Toolkit, currently in use or under consideration by life cycle practitioners, were selected for testing, and a detailed evaluation scheme was used to evaluate the effectiveness of these tools for practical application in automotive life cycle studies. A consensus numerical score for each of 20 separate test criteria was assigned to each of the software packages under evaluation, and the total scores compared. On the basis of these scores, the authors chose GaBi version 3.2 as the LCA software package currently best suited for use by experienced life cycle practitioners in conducting environmental life cycle assessments in the automotive industry.

Saturn currently injection molds and paints PPE+PA66 exterior body panels in its Spring Hill, TN facility. These manufacturing operations result in a continuous stream of waste material that needs to be responsibly and economically managed. This paper will summarize the process that General Motors and Saturn used to evaluate and validate the use of post-industrial painted PPE+PA66 reprocessed material in Saturn and General Motors' wheel trim applications (wheel covers). Not only did this project increase the amount of recycled content in General Motors' vehicles, but it also provided Saturn Corporation with a favored outlet for an internal waste stream.

A front suspension laboratory test procedure was developed to reproduce time-correlated fatigue damaging events from a light truck road durability test. Subsequently, the performance of front suspension systems for the GMT 400 light truck program were evaluated in terms of customer reliability. Both prototype and pilot testing, as well as computer modeling, were used in the evaluation.

During early 2005 General Motors released a newly developed ATF for the factory fill of all GM Powertrain stepped gear automatic transmissions. The new fluid provided significantly improved performance in terms of friction durability, viscosity stability, aeration and foam control and oxidation resistance. In addition, the fluid has the potential to enable improved fuel economy and extended drain intervals. Since the performance of the new fluid far exceeded that of the DEXRON®-III service fill fluids available at the time it became necessary to upgrade the DEXRON® service fill specification in order to ensure that similar fluids were available in the market for service and repair situations. This latest upgrade to the service fill specification is designated DEXRON®-VI [1].

From November 1970 through August 1971 an extensive program of static and dynamic air cushion inflation tests utilizing human volunteers was conducted at Holloman Air Force Base, New Mexico, sponsored by the Department of Transportation. Forty-one full cushion deployment static firings were made, with air cushion hardware and seating buck environment designed by General Motors. The static series was followed by 35 dynamic sled firings of human volunteers, beginning at 8.6 g (15.1 mph) and culminating at 21.7 g (31.5 mph). A major objective of both the static and dynamic test series was to identify changes in air-cushion design found necessary to improve its protective capability for human beings. Because of the severity of cushion deployment, one modification was made following the initial static tests: The orifice diameter size of the bag inlet was reduced from 1.0 to 0.6 in to diminish the rapidity of bag inflation. This modification proved effective in the dynamic series.

A design of experiments is used to study the effect of laser weld parameters on formability of welded blanks for two different material combinations of cold rolled (bare) steel to cold rolled steel and cold rolled steel to hot dipped galvanized steel. Critical weld parameters influencing the formability of welded blanks are identified and the optimum weld set-up condition is obtained based on formability performance and consistency of formability for laser welded blanks. The results are applied to an automotive body side frame. The robustness of welded blank production is also assessed and the final welded set-up condition for the body side frame is obtained based on both the formability of welded blanks and the robustness of welded blank production. The body side frame is successfully made from the welded blanks with this final weld set-up condition.

Since 1997, General Motors Body Manufacturing Engineering - Die Engineering Services (BME-DES) has been working jointly with our software vendor to develop and implement a parallel version of stamping simulation software for mass production analysis applications. The evolution of this technology and the insight gained through the implementation of DMP/MPP technology as well as performance benchmarks are discussed in this publication.

The complexity of designing and implementing a vehicle electrical control system for ultra fuel-efficient hybrid vehicles is significantly greater than that of a conventional vehicle. To quickly demonstrate and iterate capabilities of these vehicles, an efficient and rapid means for developing requirements, mapping these into an electrical control and communications architecture, and developing prototype systems is needed. The General Motors Precept concept vehicle is an example of an energy- efficient vehicular control system developed using a "requirements to software'' development process and electronic controller infrastructure that demonstrates these attributes. The Precept is General Motors Corporation's technology demonstration concept vehicle developed to address General Motors Corporation's commitment to the Partnership for a New Generation (PNGV) program.